The growth and thermal stability of an iron oxide overlayer on yttria-stabilized zirconia (YSZ) have been studied using atomic layer deposition (ALD), mainly in combination with low-energy ion scattering (LEIS). These techniques form a powerful combination, where ALD is designed for controlled (sub)monolayer deposition, while LEIS selectively probes the altered outermost atomic layer. The Fe(acac)(3) precursor reacts already at room temperature with YSZ. The reaction proceeds until saturation, which is characteristic for ALD. After the results of repeated ALD cycles, which consist of Fe(acac)(3) deposition followed by an oxidation treatment, have been studied, a model could be proposed which describes the growth mode of the iron oxide layer on YSZ. Oxidation at temperatures of 800 degreesC and higher causes a migration of Fe2O3 into the bulk, limiting its usefulness in surface catalytic processes at these temperatures. At 800 T the diffusion coefficient of Fe in YSZ is determined to be 10(-23) m(2)/S. The reaction mechanism of Fe(acac)(3) with the YSZ surface is studied using infrared diffuse reflectance. The results reveal more than one reaction mechanism, but there seems to be a preference for the reaction via coordinatively unsaturated sites.